Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$51.78	7.797%	$55.8173	$55.82	$55.80	$55.80
Purchase #2	$52.62	13.525%	$59.7369	$59.74	$59.75	$59.70
Purchase #3	$56.47	5.288%	$59.4561	$59.46	$59.45	$59.50
Purchase #4	$138.59	12.521%	$155.9429	$155.94	$155.95	$155.90
Purchase #5	$48.46	8.371%	$52.5166	$52.52	$52.50	$52.50
Purchase #6	$100.82	7.791%	$108.6749	$108.67	$108.65	$108.70
Purchase #7	$184.77	9.455%	$202.24	$202.24	$202.25	$202.20
7 purchase totals =	$633.51		$694.3847	$694.39	$694.35	$694.30